Achy Breaky Heart

The human heart does not like surprises. In the month after 9/11, incidents of dangerous heart rhythms in cardiac patients around New York City more than doubled. After a major earthquake in Taiwan in 1999, hospitalization for heart attacks skyrocketed around the epicenter. Even an isolated, private event  the sudden death of a spouse, for instance  can bring on grief so severe that sometimes our hearts, quite literally, break.

We all know the shock of the unexpected is stressful. And researchers have long suspected that stress harms the body. But partly because...